Horticulture Guy"Live Long and Garden" – Peter Punzi

Q. As you suggested in The News Tribune in February, instead of spraying my apple tree for apple maggot this year, I ordered and used nematodes. What a beautiful LOOKING crop of apples I have, but have not been able to salvage even one apple from the apple maggot (compared to only 5 apples infected last year after spraying.) Please tell me how to dispose of this large crop of infected apples so as to reduce next year’s infestation, i.e. spray, cook, bury, put in yard waste recycle bin? Laurice Hanson – Lakewood, WA

A. I believe you are referring to my answer to a question from William Thompson of Tacoma where I mentioned multiple strategies for control that should be used in conjunction with each other. The first suggestion was bagging the fruit. This may seem an impossible task on a large tree but even if you had bagged a few dozen you would have at least had some fruit this year. This prevents the apple maggot fruit flies from gaining access to lay eggs under the skin of the fruit. If done properly there is 100% control.

The reason I didn’t suggest spraying is that the appropriate timing is difficult for the home grower. Timing is critical since once the flies have laid their eggs not spray can reach the eggs and developing larvae below the skin of the fruit. I have seen suggestions for Kaolin spray, which is a non-toxic clay based product. It has received mixed reviews. I think the reason is because the efficacy depends on cloaking the tree and its fruit with the dust. In addition to cloaking the tree the dust is supposed to irritate the flies.

Kaolin does not actively control apple maggot flies and if it is used in that manner it will not be effective. As you mention I also suggested beneficial nematodes. I also mentioned that nematodes should be labeled for control of apple maggots. Not all species of beneficial nematodes will work. Steinernema feltiae is a species that is labeled to control apple maggot larvae. The nematodes are applied to the soil below the dripline of the tree when the larvae are present. As a side note I would also like to see some research done on soil drenches with neem oil since I think this may be another control.

Currently I do not know of any neem products that are labeled for use on apple maggot larvae or any studies being conducted. In addition I mentioned putting up baited sticky traps. These will not control a full on assault but if you have controlled your immediate population they will get most of the flies that may move in from other areas. Flies can travel as far as a quarter to a half-mile. So even if you eradicate the population in the yard you may still have incursions from other apple trees or other hosts like hawthorns growing in the area.

Right now you should have tarps below the tree to catch the fruit, or pick it all off. When recommendations are made for destroying the fruit what they are really saying is destroy the larvae and keep them from reaching soil. Rarely is it explained what destroying entails so I will give you some alternatives. One alternative is to grind the fruit in a garbage disposal. Packing off whole fruit in the organic recycling bin may is also an option but I would find out where your recyclable yard waste is taken. If it is within ½ a mile of any apple growers this is not an option. Don’t forget there are lots of people making a living growing apples and apple maggots are devastating to them. Boiling of the fruit is another option which may be more difficult to achieve. Boiled fruit can then be composted since the larvae are killed by the heat. My point is to be persistent and implement multiple strategies.
Other useful tools form monitoring and controlling apple maggots are: Apple Maggot Lures and APPLE MAGGOT TRAP and LURE.